The present invention relates to a light aircraft employing a parachute wing. A parachute wing has a fabric parachute canopy which assumes an aerofoil section shape in flight. The shape of the canopy is maintained by air flow, the canopy having no rigid struts, and lift is generated by forward motion of the aerofoil shaped canopy. The pilot sits in a carriage suspended in flight from the parachute-wing and motive power is provided by an engine-driven propeller mounted on the carriage.
Objects of the invention are to provide a light aircraft of the kind described which is inexpensive, easy to fly, and safe. A particular advantage of the parachute-wing aircraft is that the wing may be packed into a particularly compact bag since there are no rigid struts. A feature of the invention is the design of a fold-up carriage which is simple to erect and which may be stowed in a compact form.
Powered parachute-wing aircraft have been suggested hithereto, but no machine has been disclosed which provides satisfactory solutions to certain practical problems. Two closely associated problems are those of control of the wing and the effect of propeller torque reaction. The effect of propeller torque reaction is to tend to twist the engine, and thus the carriage, in a direction opposite to that of the propeller rotation. While this effect is negligible in a rigid-wing aircraft of significant weight, it is significant in a light, parachute-wing aircraft. This torque has the effect of exerting a differential left-right tension on the support lines, and therefore unbalancing the aircraft and affecting control, particularly if control is by means of control lines extending from the canopy to the carriage.
Earlier discussion of powered parachute-wing aircraft have not addressed this problem. For example, U.S. Pat. Nos. 3,343,779 and 4,375,280 have shown schematic arrangement for supporting a propeller-driven load from a parachute wing. The earlier specification has no discussion of directional control and shows suspension of the load from a single suspension point. If there were to be any directional control with such an arrangement, since the disposition of the load with respect to the wing is uncontrollable, this would have to be effected by a rudder on the load.
Such an arrangement is indeed suggested in U.S. Pat. No. 4,375,280 (U.S. Pat. No. '280). Again, in the majority of embodiments the load or carriage is supported at a single point from a free wing which may be rigid or partly flexible. There is discussion in U.S. Pat. No. '280 of a two-point suspension system to allow the altitude of the carriage to be controlled with respect to the wing, but no discussion of the effect of torque reaction.
Compensation for the effect of torque reaction is possible by the use of contra-rotating propellers. A two-propeller machine is disclosed, for example, in U.S Pat. No. 4,424,945. However, here there is also a rigid wing in addition to a parachute wing and the purpose of the second propeller and engine is said to be for additional power. There is no discussion of torque reaction.
Contra-rotating propeller arrangements are heavy and expensive. Also, the provision of flaps and rudders on the carriage is unduly complex, adds to the weight and is expensive.